Here is a simple and brief breakdown of how I would go about this training:
Get the dog used to being on the board at home by having him sit and do tricks on it, always giving him the treat while he is on the board.
Have your dog stay on the board for long periods of time.
Slowly introduce distractions so your dog stays on the board even around seagulls, seals, whales, oh my!
Having your dog stand on the board while you move it, either dragging it (if it's an old, unused board) or carrying it.
Having your dog float on the board in calm water,such as a lake.
And finally, applying all of this in the ocean.
It seems this would take many months of slow, progressive training to accomplish.. I'm excited to see if any of my dogs will be willing to surf next week.